RF power amplifiers, under the current state of technology, consist of a power transistor package directly mounted to the main amplifier heat sink as well as connected to the printed circuit board (PCB). FIG. 1 shows a typical basic arrangement 100. Shown are a section of the main amplifier heat sink 110, sections of the amplifier PCB 130a and 130b and the RF power transistor 140. The RF power package also has its own integral heat sink 120. FIG. 2 shows the RF power package 140 minus the lid. The basic package consists of the base heat sink 120 onto which is attached the dielectric insulator frame 150 onto which in turn is attached the input (gate) 170a and output (drain) 170b leads, and both electrical contacts to the power amplifier system. The heat sink 120 acts as the source contact for the transistor device. To complete the device, thinned transistor die 160 plus capacitors are eutectically attached to the heat sink 120. These in turn are wired to each other as well as to the leads 170. Finally a lid is placed onto the package leaving an open cavity transistor device package. This creates a multi-chip module arrangement. FIG. 3 depicts a recess 190 with bolt holes which are often machined into the main heat sink 110 needed to receive the RF power package 140. In the assembly process for the amplifier, the PCB sections 130a and 130b are attached to the main heat sink 110. The RF transistor package 140 is then bolted to the heat sink 110 to make thermal and electrical contact, as shown in FIG. 1. The leads 170a and 170b are, respectively, soldered to the PCB sections 130a and 130b. 
The RF power amplifier described above has limitations, especially in regards to the thermal management of the heat generated by the RF power transistor chip 160. The RF power transistor package 140 and its heat sink base 120 are designed to account for the expansion characteristics of the silicon die. This leads to compromises in the thermal conductivity of the package heat sink 120 as well as higher cost. Also the mechanical interface between the package heat sink 120 and the main heat sink 110 can have degraded thermal conductivity if areas of low conductivity or gaps are present in metal-to-metal contact regions. The mounting hardware also increases cost for the amplifier manufacturer. In some cases the package heat sink 120 is soldered directly to the main heat sink 110. This method has reliability concerns due to the expansion characteristics of the heat sinks and the solder, which in turn impacts thermal performance.